more stuff working

naga/src/front/wgsl/error.rs

@@ -260,6 +260,13 @@ pub(crate) enum Error<'a> {
         expected: Range<u32>,
         found: u32,
     },
+    WrongArgumentCountForOverloads {
+        function: String,
+        call_span: Span,
+        arg_span: Span,
+        max_arguments: u32,
+        overloads: Vec<String>,
+    },
     WrongArgumentType {
         function: String,
         call_span: Span,
@@ -821,6 +828,27 @@ impl<'a> Error<'a> {
                 labels: vec![(span, "wrong number of arguments".into())],
                 notes: vec![],
             },
+            Error::WrongArgumentCountForOverloads {
+                ref function,
+                call_span,
+                arg_span,
+                max_arguments,
+                ref overloads,
+            } => {
+                let message = format!(
+                    "For the preceding argument types, `{function}` accepts only {max_arguments} arguments"
+                );
+                let labels = vec![
+                    (call_span, "This function call has too many arguments".into()),
+                    (arg_span, "This is the first excess argument".into())
+                ];
+                let mut notes = vec![
+                    format!("These are the only overloads of `{function}` that could accept the preceding arguments:"),
+                ];
+                notes.extend(overloads.iter().map(|o| format!("overload: {o}")));
+
+                ParseError { message, labels, notes }
+            }
             Error::WrongArgumentType {
                 ref function,
                 call_span,

naga/src/front/wgsl/lower/mod.rs

@@ -2298,20 +2298,52 @@ impl<'source, 'temp> Lowerer<'source, 'temp> {
                     use crate::proc::Rule as _;
 
                     let mut overloads = fun.overloads();
+                    log::debug!("JIMB: {fun:?}");
+                    let min_arguments = overloads.min_subexpressions();
+                    let max_arguments = overloads.max_subexpressions();
+                    if arguments.len() < min_arguments || max_arguments < arguments.len() {
+                        return Err(Error::WrongArgumentCount {
+                            span,
+                            expected: min_arguments as u32 .. max_arguments as u32,
+                            found: arguments.len() as u32
+                        });
+                    }
+
                     let mut unconverted_arguments = Vec::with_capacity(arguments.len());
                     for (i, &arg) in arguments.iter().enumerate() {
                         let lowered = self.expression_for_abstract(arg, ctx)?;
                         let ty = resolve_inner!(ctx, lowered);
                         let remaining_overloads = overloads.arg(i, ty, &ctx.module.types);
                         if remaining_overloads.is_empty() {
-                            return Err(Error::WrongArgumentType {
-                                function: fun.to_wgsl().to_string(),
-                                call_span: span,
-                                arg_span: ctx.ast_expressions.get_span(arg),
-                                arg_index: i as u32,
-                                found: crate::common::wgsl::Wgslish(ty).to_string(),
-                                allowed: overloads.allowed_args(i),
-                            });
+                            // If there were other types permitted for the i'th arg, then
+                            // this is a no-such-overload error.
+                            //
+                            // Otherwise, since we checked the argument count against the
+                            // min and max earlier, it must be the case that the prior
+                            // arguments narrowed the overloads to a subset none of which
+                            // accept this many arguments.
+                            let arg_span = ctx.ast_expressions.get_span(arg);
+                            let allowed = overloads.allowed_args(i);
+                            let function = fun.to_wgsl().to_string();
+                            if allowed.is_empty() {
+                                let overload_list = overloads.overload_list(&function);
+                                return Err(Error::WrongArgumentCountForOverloads {
+                                    function,
+                                    call_span: span,
+                                    arg_span,
+                                    max_arguments: overloads.max_subexpressions() as u32,
+                                    overloads: overload_list,
+                                });
+                            } else {
+                                return Err(Error::WrongArgumentType {
+                                    function,
+                                    call_span: span,
+                                    arg_span,
+                                    arg_index: i as u32,
+                                    found: crate::common::wgsl::Wgslish(ty).to_string(),
+                                    allowed,
+                                });
+                            }
                         }
                         overloads = remaining_overloads;
                         unconverted_arguments.push(lowered);

naga/src/proc/builtins/list.rs

@@ -84,16 +84,22 @@ impl super::OverloadSet for List {
         self.members == 0
     }
 
-    fn min_subexpressions(&self) -> Option<usize> {
-        self.members().fold(None, |n, (_, rule)| {
-            std::cmp::min(n, Some(rule.subexpressions.len()))
-        })
+    fn min_subexpressions(&self) -> usize {
+        self.members().fold(None, |best, (_, rule)| {
+            // This is different from `max_subexpressions` because
+            // `<Option as PartialOrd>` doesn't work the way we'd like.
+            let len = rule.subexpressions.len();
+            Some(match best {
+                Some(best) => std::cmp::max(best, len),
+                None => len
+            })
+        }).unwrap()
     }
 
-    fn max_subexpressions(&self) -> Option<usize> {
+    fn max_subexpressions(&self) -> usize {
         self.members().fold(None, |n, (_, rule)| {
             std::cmp::max(n, Some(rule.subexpressions.len()))
-        })
+        }).unwrap()
     }
 
     fn arg(&self, i: usize, ty: &crate::TypeInner, types: &crate::UniqueArena<crate::Type>) -> Self {
@@ -122,7 +128,8 @@ impl super::OverloadSet for List {
     }
 
     fn most_preferred(&self) -> Option<Rule> {
-        self.members().next().map(|(_, rule)| rule.clone())
+        let (_, rule) = self.members().next().unwrap();
+        Some(rule.clone())
     }
 
     fn overload_list(&self, name: &str) -> Vec<String> {

naga/src/proc/builtins/mod.rs

@@ -25,12 +25,20 @@ pub trait OverloadSet: Clone + std::fmt::Debug {
     fn is_empty(&self) -> bool;
 
     /// Return the smallest number of subexpressions in any type rule
-    /// in the set. Return `None` if `self` is empty.
-    fn min_subexpressions(&self) -> Option<usize>;
+    /// in the set.
+    ///
+    /// # Panics
+    ///
+    /// Panics if `self` is empty.
+    fn min_subexpressions(&self) -> usize;
 
     /// Return the largest number of subexpressions in any type rule
-    /// in the set. Return `None` if `self` is empty.
-    fn max_subexpressions(&self) -> Option<usize>;
+    /// in the set.
+    ///
+    /// # Panics
+    ///
+    /// Panics if `self` is empty.
+    fn max_subexpressions(&self) -> usize;
 
     /// Limit `self` to the overloads that can accept a given
     /// subexpression.
@@ -78,12 +86,15 @@ pub trait OverloadSet: Clone + std::fmt::Debug {
     /// [concretize]: https://gpuweb.github.io/gpuweb/wgsl/#concretization
     fn concrete_only(self, types: &crate::UniqueArena<crate::Type>) -> Self;
 
-    /// Return the most preferred candidate, or `None` if `self` is empty.
+    /// Return the most preferred candidate.
     ///
     /// Rank the candidates in `self` as described in WGSL's [overload
     /// resolution algorithm][ora], and return a singleton set containing the
     /// most preferred candidate.
     ///
+    /// If there is no most preferred candidate, return `None`,
+    /// indicating that the expression is ambiguous.
+    ///
     /// As it's described in the spec, choosing the most preferred candidate
     /// depends on the ranks of the conversions being applied to each argument,
     /// so it's impossible to determine the most preferred candidate from the
@@ -93,6 +104,10 @@ pub trait OverloadSet: Clone + std::fmt::Debug {
     /// leaf scalar type for all its subexpressions, then the most abstract
     /// overload must be the most preferred candidate.
     ///
+    /// # Panics
+    ///
+    /// Panics if `self` is empty.
+    ///
     /// [ora]: https://gpuweb.github.io/gpuweb/wgsl/#overload-resolution-section
     fn most_preferred(&self) -> Option<Self::Rule>;
 
@@ -139,13 +154,13 @@ impl OverloadSet for AnyOverloadSet {
         }
     }
 
-    fn min_subexpressions(&self) -> Option<usize> {
+    fn min_subexpressions(&self) -> usize {
         match *self {
             AnyOverloadSet::List(ref list) => list.min_subexpressions(),
         }
     }
 
-    fn max_subexpressions(&self) -> Option<usize> {
+    fn max_subexpressions(&self) -> usize {
         match *self {
             AnyOverloadSet::List(ref list) => list.max_subexpressions(),
         }
@@ -165,7 +180,7 @@ impl OverloadSet for AnyOverloadSet {
 
     fn most_preferred(&self) -> Option<AnyRule> {
         match *self {
-            AnyOverloadSet::List(ref list) => list.most_preferred().map(AnyRule::List),
+            AnyOverloadSet::List(ref list) => list.most_preferred().map(AnyRule::List)
         }
     }
 
@@ -216,6 +231,10 @@ impl crate::MathFunction {
         const VEC3F: Ti = Ti::Vector { size: Vs::Tri, scalar: Sc::F32 };
         const VEC4F: Ti = Ti::Vector { size: Vs::Quad, scalar: Sc::F32 };
 
+        const VEC2AF: Ti = Ti::Vector { size: Vs::Bi, scalar: Sc::ABSTRACT_FLOAT };
+        const VEC3AF: Ti = Ti::Vector { size: Vs::Tri, scalar: Sc::ABSTRACT_FLOAT };
+        const VEC4AF: Ti = Ti::Vector { size: Vs::Quad, scalar: Sc::ABSTRACT_FLOAT };
+
         const VEC2I: Ti = Ti::Vector { size: Vs::Bi, scalar: Sc::I32 };
         const VEC3I: Ti = Ti::Vector { size: Vs::Tri, scalar: Sc::I32 };
         const VEC4I: Ti = Ti::Vector { size: Vs::Quad, scalar: Sc::I32 };
@@ -266,9 +285,29 @@ impl crate::MathFunction {
             },
         ];
 
+        static POW: &[list::Rule] = &[
+            list::Rule {
+                subexpressions: &[Ti::Scalar(Sc::F32), Ti::Scalar(Sc::F32)],
+                conclusion: Ti::Scalar(Sc::F32),
+            },
+            list::Rule {
+                subexpressions: &[Ti::Scalar(Sc::ABSTRACT_FLOAT), Ti::Scalar(Sc::ABSTRACT_FLOAT)],
+                conclusion: Ti::Scalar(Sc::ABSTRACT_FLOAT),
+            },
+            list::Rule {
+                subexpressions: &[VEC2F, VEC2F],
+                conclusion: VEC2F,
+            },
+            list::Rule {
+                subexpressions: &[VEC2AF, VEC2AF],
+                conclusion: VEC2AF,
+            },
+        ];
+
         match self {
             Mf::Sin => AnyOverloadSet::List(list::List::from_rules(COMPONENT_WISE_FLOAT)),
             Mf::Dot => AnyOverloadSet::List(list::List::from_rules(DOT_PRODUCT)),
+            Mf::Pow => AnyOverloadSet::List(list::List::from_rules(POW)),
             _ => todo!(),
         }
     }